Make this jam with only the most flavorful melons. We like to use fragrant Charentais melons when we can find them. Please read How to Process.
Prepare a water-bath canner, gather all your canning equipment, place a couple of saucers in the freezer, and have ready 3 clean, hot half-pint jars.
Combine in a heavy pot:
Bring to a boil and boil rapidly, stirring frequently, until it reaches the jelling point. Remove from the heat. Fish out the vanilla bean, if using, scrape any vanilla seeds from the pod and add them back to the pot, then discard the pod. Ladle jam into the prepared jars, leaving ¼ inch headspace. Wipe the rims. Place lids on jars and screw on rings until fingertip-tight. Process for 10 minutes. Let cool completely and store as directed.